Bioplastic nanocomposite – PLA, PiFM and Ecology

With global attention on the role that plastics play in our ecosystem, many researchers are investigating new bioplastic or “biodegradable polymer” alternatives to reduce the ecological impact of plastic packaging. One such promising thermoplastic is polylactic acid (PLA). This bioplastic decomposes into lactic acid and can be derived from renewable resources like corn starch or sugar cane during starch fermentation. PLA is widely applicable, cost-efficient to produce and degrades naturally in the environment under certain conditions. For this reason, PLA is found in many consumer products, such as medical implants, 3D printing, and disposable and compostable cups and plates.

Research groups are currently testing its degradability under realistic and natural conditions, including marine waters, soil and compost. In order to degrade, heat and moisture are required for hydrolyzing to occur. There are some disadvantages in the material properties of PLA, primarily in the form of gas permeability and mechanical properties. PLA is typically soft and has a high transmission rate of gases, making it difficult to use for food storage. Additionally, the ease with which PLA melts makes it unsuitable to hold hot liquid. Engineering ways to strengthen the material will aid in its adoption.

Here we study the nanocomposition of PLA with an alkyl acrylate copolymer (ACM or Acrylic rubber) using PiFM to determine how the materials are dispersed. Using the excellent correlation between PiFM and FTIR spectra, we are able to confidently show where the two materials are located within the material matrix with nanometer spatial resolution.

Polylactic Acid (PLA) – Alkyl Acrylate Copolymer (ACM) Composite

Bioplastic: PiFM images of Polylactic Acid (PLA) - Alkyl Acrylate Copolymer (ACM) Composite

Figure 1: Fixed wavenumber PiFM imaging of the PLA-ACM composite. The polylactic acid is highlighted at 1750 cm-1 (blue) and the acrylic rubber is highlighted at 1720 cm-1 (green). We noticed a unique third component with an absorption at 1070 cm-1 (red), different from the spectral responses for the PLA and ACM components. The PiFM images are combined and overlayed on the 3D topographic image (on the left).

Bioplastic: High resolution spectrum of third component found in PiFM image of Polylactic Acid (PLA) - Alkyl Acrylate Copolymer (ACM) Composite

Figure 2: High resolution spectra of all three components. The combined PiFM image follows the same color key as Figure 1. We are able to highlight spectral differences with a high degree of correlation with known FTIR spectra of the PLA and ACM components. Note that the point spectrum on the red spot (third component) shows a unique spectrum from an area only 60 nm across.

To view a video demonstration of the imaging session for the data presented here, please follow this link: EP2: PiFM @ Work – Polylactic Acid and Acrylic Rubber Nano Composite

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